This invention relates generally to the solar heating art and more particularly to a novel solar heating panel arrangement and method wherein solar radiation is focused by a plurality of spherical lenses for transfer to a fluid in the form of heat.
There have heretofore been proposed several types of solar heating panels for absorbing energy from the sun and transferring it to a fluid passed through the panels. The heated fluid may generally be either a fluid such as water for consumption in a heated state or a recirculating fluid fo transfer of thermal energy from the solar panel to another device. In cases where consumable fluid is heated, the fully heated fluid may be passed to an insulated reservoir for storage until needed.
Prior solar heating panels often incorporate a plurality of fluid-carrying pipes or other conduits directly exposed to the sun's radiation. A portion of the incident radiation is thus absorbed by the pipes in the form of heat, and a portion of that heat is transferred to the fluid. While panels of this type cause the temperature of the fluid to increase, the efficiency of such panels suffers substantially from limitations on heat transfer between the pipes and the fluid passing therethrough. Since the amount of heat transferred from one element to another is directly related to the temperature gradient between the two elements, heat transfer from pipes uniformly heated by the sun is limited by the relatively low uniform pipe temperatures obtainable through solar irradiation. Solar panels of this type may also be limited in efficiency by an inherent dependence of their operating characteristics on the relative position of the sun. As the sun moves across the sky through the course of a day, the amount of solar radiation reaching the pipes or other conduits may fall far below the desired level.
Tracking mechanisms have been proposed for changing the orientation of solar panels during the day to follow the sun as it crosses the sky, however, such mechanisms are themselves wasteful of energy and considerably complicate solar heating systems.
U.S. Pat. No. 1,093,498 issued to Thring discloses a solar heating panel having an array of spherical lenses projecting into hemispherical recesses formed in the upper surface of a water tank and separated from the surfaces of the recesses by a relatively small distance. Solar radiation incident on the spherical lenses is directed onto the surfaces of the hemispherical recesses for the various positions of the sun. However, the volume of water in the tank is substantial and the flow path near the top of the tank is relatively obstructed, causing the fluid flow rate past many points in the tank to be very slow. At those points, heated fluid would tend to remain near the location at which it picked up its heat, reducing the temperature differential between the recesses and the fluid. The rate of heat transfer would thus be reduced, as well.
U.S. Pat. No. 4,056,093 issued to Barger discloses a solar heater having a single spherical lens positioned over a thin hemispherical flow passage for heating a fluid therein. The lens is positioned under a transparent hemispherical cover which insulates the lens assembly against heat dissipation to the atmosphere. However, any cover of the type disclosed would permit substantial amounts of heat to be lost.
In addition, each lens of the Thring and Barger patents is able to produce only a single heated area on the corresponding hemispherical surface, that area representing the solar radiation which is directly incident on the lens. The amount of heat transferred to the fluid is thus severely limited by the size of the lenses used.
Therefore, it is desirable to provide a solar heating panel able to more efficiently convert incident solar radiation to usable thermal energy stored in a fluid.